Fixes broken build introduced in last commit by adding a seemingly unnecessary cast; JDT doesn't need it, but javac breaks without it. This needs Scott to come back and verify the change.

Review by: scottb (TBR)

git-svn-id: https://google-web-toolkit.googlecode.com/svn/releases/1.6@4734 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/dev/core/src/com/google/gwt/dev/javac/JsniChecker.java b/dev/core/src/com/google/gwt/dev/javac/JsniChecker.java
index 393bedd..38332fa 100644
--- a/dev/core/src/com/google/gwt/dev/javac/JsniChecker.java
+++ b/dev/core/src/com/google/gwt/dev/javac/JsniChecker.java
@@ -209,7 +209,7 @@
         ProblemReferenceBinding prb = (ProblemReferenceBinding) binding;
         if (prb.problemId() == ProblemReasons.NotVisible) {
           // It's just a visibility problem, so try drilling down manually
-          ReferenceBinding drilling = prb.closestMatch();
+          ReferenceBinding drilling  = (ReferenceBinding) prb.closestMatch();
           for (int i = prb.compoundName.length; i < compoundName.length; i++) {
             drilling = drilling.getMemberType(compoundName[i]);
           }